The invention relates to a technique of distributing loads when a frame is sent/received between terminals within a communication network.
In recent years, a general LAN (Local Area Network) network has improved so much that information can be transmitted therethrough over an increasing distance. Accordingly, it becomes possible to use a network adopting the LAN in a wide range area as compared with the conventional use in as narrow a range as within premises.
Further, a LAN technology for use in a wide range area allows a communications provider (carrier) to provide a service to provide LAN network communications whose typical examples include a wide-area LAN service. The LAN technology also allows an ISP (Internet Services Provider) to use a LAN to build a regional network serving as a service network for connection to the Internet.
Even in the case where the communications provider operates business using such a LAN network, which may cause expansion of access areas or connections made by an indefinite number of subscribers, there is a demand for a load distribution function equivalent to a function performed in the conventional LAN network through an upper protocol.
In addition, for expansion of the LAN network, instead of expansion using a simple layer 2 switch, there is provided a technology in which MPLS (Multi Protocol Label Switching) is used to encapsulate a frame and an MPLS network, such as a VPLS (Virtual Private LAN Segment), is set as a single switch.
In terms of a process of distributing loads within a network, there is provided a device for a load distribution process such as MPLS-TE (Terminal Equipment). In terms of a filter function used for a load distribution process, there is provided a device having, for example, a MAC (Media Access Control) address filtering function. The functions for performing such a load distribution process include identification of a traffic that is flowing. The functions also include selection of a path that is logically equal to and physically different from the original path depending on an attribute of the traffic.
In the LAN network technology, a load distribution key (load distribution information) is used for identification of the traffic attribute. The load distribution key is obtained by applying distribution to MAC addresses indicating the source/destination of a traffic frame based on a hash calculation. This is because the load distribution key allows equal distribution owing to a statistical multiplexing effect when the number of combinations of MAC addresses increases to some extent.
Alternatively, as a method of distributing loads in a network upper than a LAN network, there is a method of setting a logical address defined in the upper network as the load distribution key.
Note that as the prior art relating to the invention, there is, for example, a technique as disclosed in Patent document 1 described below.
[Patent Document 1] JP 2000-13439 A